1. Field of the Invention
The present invention relates to a colored and fired film and a method for producing the same. More specifically, the present invention relates to a colored and fired film having excellent chemical resistance formed on a transparent substrate such as a glass plate, and a method for producing the same.
2. Description of the Prior Art
As a method for coloring a surface of a glass substrate, the following method is commonly used. A mixture of glass powder and a coloring agent is applied onto the surface of a glass substrate by printing, and then fired. This method provides an excellent design, because a coloring agent can be applied to the glass substrate as desired. However, light is scattered at the melting interface of the glass powder, so that the parallel transmittance of light is 80% or less. Therefore, this method is not suitable for producing a transparent colored film.
In order to produce a transparent colored film on a glass substrate, several methods have been proposed. One of the methods is referred to as an ion exchange method, in which a specific inorganic salt comprising Ag, Cu and the like is applied to the surface of the glass substrate, and fired. Thereafter, an oxide attached to the surface of the glass substrate is removed by washing. Then, the ultra-fine particles of Ag and Cu in the inorganic salt that have permeated the glass substrate provide colors as colloidal particles. Thus, a transparent colored film is formed on the glass substrate.
Furthermore, according to another method, a sputtering technique is used to form a metal thin film on a glass substrate.
However, the ion exchange method has a drawback in that the kinds of the colors that can be obtained are limited, because the ultra-fine particles are hardly generated by some elements. In addition, the sputtering method is disadvantageous in that the strength of the obtained film is not sufficiently high, a complicated pattern cannot be formed, and a large-scale production apparatus is required.
In view of these problems, a method has been proposed in which a glass coloring composition comprising the ultra-fine particles of a metal, an organic metal compound (a fixing agent), and a binder resin is used for coloring a glass substrate. When using this composition, the requirements for coloring the glass substrate without compromising the transparency are as follows:
(1) To select a solvent in which the ultra-fine particles of the metal can be present stably without being aggregated; PA1 (2) The organic metal compound should be dissolved in the solvent selected in (1), and should not react with the ultra-fine particles of the metal physically or chemically; and PA1 (3) The binder resin should be dissolved in the solvent selected in (1), and should not react with the ultra-fine particles of the metal physically or chemically.
More specifically, the following glass coloring compositions are known: a composition obtained by dissolving a polymer complex comprising the ultra-fine particles of gold dispersed in nylon 11, an organic metal compound (cobalt organic acid salt) and a binder resin (nylon 11) in a solvent (cresol); a composition obtained by dissolving the above-mentioned polymer complex, the organic metal compound and a binder resin (cellulose nitrate) in a solvent (carbitol); and a composition obtained by dissolving the above-mentioned polymer complex, the organic metal compound and a binder resin (ethyl cellulose) in a solvent (terpinol). These coloring compositions can color the surface of a glass plate gray in a haze ratio of 3% or less.
Furthermore, Japanese Laid-Open Patent Publication No. 7-25641 disclosed a coloring agent having improved chemical durability by adding a glass network forming component such as silicon alkoxide.
However, a colored film is desired that is hardly affected by acid rain and has a constant transmittance of light and an unchanged tone of color, even if the glass plate has been used outdoor for a long period of time.